Transmit is an excellent FTP (file transfer protocol), SFTP, S3 (Amazon.com file hosting) and iDisk/WebDAV client that allows you to upload, download, and delete files over the internet. With the most Mac-like interface available, Transmit makes FTP as simple, fun, and easy as it can possibly be.

Elegant UI, excellent functionality, occasional performance hitches; despite being a paying user for years, I've switched to YummyFTP for SFTP and vanilla FTP, because I prefer its Finder-like hierarchical view. (I do web dev for a living; I don't use Amazon S3, and avoid WebDav like the plague!) But if you're only gonna pay for one FTP app, Transmit is the one to buy!

Stable, reliable and simple. Other FTP clients are cheaper, have more features or have a slicker design. But somehow I always end up using Transmit.

I think of it as a professional tool. Expensive and boring. :-) Transmit doesn't get in your way. It gets the job done. It has the perfect feature set. It just works. What more can you want from an FTP and WebDAV client?